基于土体软支撑模型的桩—土—结构动力数值分析

发布时间：2018-06-27 15:00

本文选题：群桩-土软支撑模型 + 土-结构相互作用　；参考：《湖南大学》2015年硕士论文

【摘要】：目前实际工程抗震设计大多采用刚性基础假定,在此基础上根据经验或规范建议对结构反应进行有利的折减,但研究表明,考虑桩土柔性参与,结构周期延长并不总伴随着较小的结构动力反应,片面地强调SSI有利面会使结构计算出现较大误差而无法满足工程需要。开展桩(基础)-土-结构物相互作用体系动力数值研究,辅以振动台试验为模拟对象,从定性和量化两方面分析相互作用体系的动力响应,并有效应用于实际工程的设计和评估中具有相当的理论和工程实践意义。本文介绍了国内外桩-土-结构相互作用分析的研究历史和现状,综述了相互作用的主要研究方法以及需要解决的问题;概括介绍了常用的桩-土-结构体系简化分析模型和完全有限元模型,给出了本文采用的考虑群桩-土动力非线性相互作用的整体PGSS体系模型,并对模型中使用的ANSYS相关单元进行了简单介绍。重点介绍了基于层状土中群桩效应的土体软支撑模型,对桩(筏)-土间、桩周近域土、远域土的弹簧刚度系数和阻尼系数进行了计算推导,在此基础上,以一平面桩-土(软支撑)-框架结构相互作用体系模型为例,进行了地震动作用下的时程分析,对比固基、线性、非线性三种分析方法结果,且与现有的试验成果有良好的一致性。建立了三维纯框架和带支撑框架桩土(软支撑)-结构相互作用模型,针对不同桩土条件和不同地震作用分别进行了非线性数值分析,结果表明:在某些地震动和土-基础条件下,上部结构非线性动力反应结果可能大于固基假定情形,且桩-土软支撑模型对上部结构柔弱层位置产生影响。指出在结构抗震设计中考虑桩-土-结构动力非线性分析十分必要。基于已有的振动台试验模型参数,建立了相应的纯框架-桩土结构及带支撑框架-桩土结构模型,分别进行了动力非线性时程分析对比,并进一步的研究了下部桩基础尺寸和土层属性变化对带支撑框架-桩土相互作用体系动力反应的影响。桩基的特殊性会弱化或加强土-结构共同作用体系的一般性特点,不同的结构体系甚至会表现出新的特征。以简化非线性弹-阻单元的形式等代桩-土实体单元接触面,建立基于土体软支撑的桩-土-结构动力相互作用的简化数值分析方法,可以快速、较准确有效地进行复杂的上下部结构动力时程分析及抗震评估。
[Abstract]:At present, the earthquake resistant design of practical engineering mostly adopts the assumption of rigid foundation, and on the basis of this assumption, the structural response is reduced advantageously according to the experience or the suggestion of code. However, the research shows that the flexible participation of pile and soil is considered. The extension of structural cycle is not always accompanied by a smaller dynamic response of the structure. It is stressed that SSI favorable surface will make the calculation of the structure more error and can not meet the engineering needs. The dynamic numerical study of pile-soil-structure interaction system was carried out, and the dynamic response of the interaction system was analyzed qualitatively and quantitatively with the shaking table test as the simulation object. And effective application in practical engineering design and evaluation has considerable theoretical and engineering practical significance. This paper introduces the history and present situation of pile-soil-structure interaction analysis at home and abroad, and summarizes the main research methods and problems to be solved. The simplified analysis model and complete finite element model of pile-soil-structure system are introduced in this paper. The global PGSS system model considering the nonlinear interaction of pile group and soil is given in this paper. The related elements of ANSYS used in the model are briefly introduced. The soft bracing model of soil based on pile group effect in layered soil is introduced emphatically. The spring stiffness coefficient and damping coefficient of pile (raft) -soil, soil around pile, and remote soil are calculated and deduced, on the basis of which the spring stiffness coefficient and damping coefficient of pile (raft) -soil are calculated and deduced. Taking a plane pile-soil (soft braced)-frame structure interaction system model as an example, the time-history analysis under ground motion is carried out, and the results of fixed foundation, linear and nonlinear analysis methods are compared. It is in good agreement with the existing experimental results. A three-dimensional pile-soil (soft braced) structure interaction model of pure frame and braced frame is established, and nonlinear numerical analysis is carried out for different pile-soil conditions and different earthquakes. The results show that under some ground motion and soil-foundation conditions, the nonlinear dynamic response of superstructure may be larger than that of the assumption of fixed foundation, and the pile-soil soft bracing model has an effect on the position of soft layer of superstructure. It is pointed out that it is necessary to consider the dynamic nonlinear analysis of pile-soil-structure in seismic design of structures. Based on the parameters of the existing shaking table test model, the corresponding models of pure frame-pile-soil structure and frame-pile-soil structure with bracing are established, and the dynamic nonlinear time-history analysis and comparison are carried out respectively. The influence of the size of the bottom pile foundation and the soil properties on the dynamic response of the pile-soil interaction system with braced frame is further studied. The particularity of pile foundation will weaken or strengthen the general characteristics of soil-structure interaction system, and different structural systems will even show new characteristics. In this paper, a simplified numerical analysis method of pile-soil-structure dynamic interaction based on soft soil support is established by simplifying the interface of the pile-soil solid element in the form of nonlinear elastic-resistance element. The method can be used to analyze the pile-soil-structure dynamic interaction quickly. The dynamic time history analysis and seismic evaluation of complex upper and lower structures are carried out accurately and effectively.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU435

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